Installation Guide (5th Edition)

Guide to the Selection & Installation of Compressed Air Services

Pages 84, 85For all hoses above 10-mm bore, or where pressures exceed 7 bar, or where hose length is greater than 10 meters, a coupling should be used which has a self-venting socket which releases the downstream pressure before disconnection is possible. Alternatively, a plug having a controlled venting action should be used. These safety features prevent uncontrolled whipping of hose when its inlet end is uncoupled from the socket.

With large bore hoses of 19 mm and above, an unexpected hose failure or accidental disconnection of a tool or fitting can cause a dangerous situation to arise because the sudden increase in air flow can result in the whipping of hose; also the sudden loss of pressure can cause a hazard elsewhere in the system.

To prevent this, a flow limiting valve should be fitted between rigid piping and the inlet end of the hose. This valve automatically closes should an excessive flow condition develop and will remain closed until normal conditions are restored.

In Other WordsA coupling with a self-venting socket that releases downstream pressure before disconnection should be used for hose above 10-mm bore or with pressures over 7 bar.